It's well known that in regulable drive shaft torque electric tool a knob is set on the outside of drive shaft. By engaging with the machine components inside the tool, knob may regulate drive shaft torque. Moreover, a torque scale is set on electric tool to regulate the need output torque with knob in which a pointer is installed. The pointer and the torque scale may read out drive shaft torque.
In early time, electric tool knob cannot rotate around 360.degree. in same direction. The rotating is along low torque level to high torque level. When knob is in the highest torque level, knob should be rotated in opposite direction for going to low torque level. Therefore, it's need to move along a long distance and inconvenient for use. The present invention is to provide a switch device for solving the said drawback.